Semiconductor device and manufacturing method thereof

ABSTRACT

It is an object of the present invention to provide a peeling method that causes no damage to a layer to be peeled and to allow not only a layer to be peeled with a small surface area but also a layer to be peeled with a large surface area to be peeled entirely. Further, it is also an object of the present invention to bond a layer to be peeled to various base materials to provide a lighter semiconductor device and a manufacturing method thereof. Particularly, it is an object to bond various elements typified by a TFT, (a thin film diode, a photoelectric conversion element comprising a PIN junction of silicon, or a silicon resistance element) to a flexible film to provide a lighter semiconductor device and a manufacturing method thereof.

TECHNICAL FIELD

The present invention relates to a peeling method of a layer to bepeeled, especially, a method for peeling a layer to be peeled includingvarious elements. In addition, the present invention relates to asemiconductor device that has a semiconductor integrated circuit or athin film transistor (hereinafter referred to as TFT) transferred bysticking a separated layer to be peeled to a substrate, and amanufacturing method thereof. The invention relates, for example, anelectro-optical device typified by a liquid crystal module, alight-emitting device typified by an EL module, and an electronics thathas such a device mounted as a component.

In the specification, the term, ‘semiconductor device’, generallyindicates devices that are capable of functioning by utilizingsemiconductor characteristics, and an electro-optical device, alight-emitting device, a semiconductor circuit, and electronics are allincluded in the semiconductor device.

BACKGROUND ART

Recently, attention has been paid to a technique of composing asemiconductor integrated circuit or a TFT using a semiconductor thinfilm on an insulating substrate such as a glass or quartz substrate. TheTFT is widely applied to electronic devices such as IC and anelectro-optical device, and has been rapidly developed especially as aswitching element of an image display device.

There are various applications of such an image display device such as adigital video camera and a liquid crystal television, and the imagedisplay device is expected to be applied to mobile electronics such as acellular phone, a portable game machine, a portable television, or aportable terminal especially for the future. As characteristics requiredby users for these mobile electronics, points of being light and beingdurable in order not to break when dropped, for example, are given.

However, the substrate used for the previous image display device is asubstrate comprising an inorganic material such as a glass substrate ora quartz substrate, as described above, and there are defects ofbreaking and being heavy, which are unique to the inorganic material. Inorder to overcome the defects, the formation of a TFT on a substratewith plasticity, typified by a flexible plastic film, has been tried.

Compared to the substrate such as the glass or quartz substrate,however, the substrate such as the plastic film has low heat resistance,and therefore, a processing temperature in manufacturing a TFT islimited. In the result, it was difficult to manufacture a TFT directlyon the plastic film, which has favorable characteristics compared to theTFT formed on the glass or quartz substrate. Consequently, ahigh-performance image display device or light-emitting device that usesa plastic film has not been realized.

Recently, a peeling method for peeling a layer to be peeled existingover a substrate with a separating layer interposed therebetween, hasalready been proposed. For example, Japanese Patent Laid-Open No.10-125929 and Japanese Patent Laid-Open No. 10-425931 describe atechnique of separating a substrate by providing a separating layer ofamorphous silicon (or polycrystalline silicon) and irradiating a laserbeam through the substrate to release hydrogen contained in theamorphous silicon to form pores. In addition, Japanese Patent Laid-OpenNo. 10-125930 gives a description of sticking a layer to be peeled (inthe publication, called a layer to be transferred) on a plastic layerwith the use of this technique to complete a liquid crystal displaydevice.

However, since amorphous silicon or polycrystalline silicon is used asthe separating layer in the aforementioned method, a problem isconsidered that an irradiated laser beam is transmitted through theseparating layer depending on a film thickness thereof and a wavelengthof the applied laser beam to damage the layer to be peeled. Further, inthe aforementioned method, in the case of forming an element on aseparating layer, hydrogen contained in the separating layer is diffusedand decreased when a heat treatment at a high temperature is carried outin the process of manufacturing the element. As a result, there is thepossibility of insufficient peeling even if the separating layer isirradiated with a laser beam. Therefore, there is a problem that theprocess after forming the separating layer is limited in order to retainof the amount of hydrogen contained in the separating layer.Additionally, it is difficult to peel a layer to be peeled with a largesurface according to the aforementioned method. Although theaforementioned publication gives a description of forming alight-shielding layer or a reflection layer in order to prevent thelayer to be peeled from being damaged, in that case, it becomesdifficult to fabricate a transmission type liquid crystal displaydevice.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

The present invention has been accomplished in view of theaforementioned problems, and it is an object to provide a method thatenables peeling without damaging a layer to be peeled and to allow notonly a layer to be peeled with a small surface area but also a layer tobe peeled with a large surface area to be peeled entirely.

Further, it is also an object of the present invention to provide alighter semiconductor device and a manufacturing method thereof bysticking a layer to be peeled on a variety of substrates. Especially, itis an object of the present invention to provide a lighter semiconductordevice and a manufacturing method thereof by sticking a variety ofelements typified by a TFT (a thin film diode, a photoelectricconversion element comprising PIN junction of silicon, and siliconresistor element) on a flexible film.

Means for Solving the Problem

With a large number of experiments and considerations made repeatedly,the inventors have found a method for peeling an element such as a TFTfrom a substrate, wherein after providing an oxide layer in contact withthe metal layer provided over a substrate and further providing variouselements such as a TFT on the oxide layer, the metal layer is oxidizedto perform peeling completely with a physical means, typically, applyingmechanical force (for example, peeling with a hand) within a metal oxidelayer formed or at an interface (an interface between the metal oxidelayer and the oxide layer).

Properties of a material vary greatly depending on a state of aconfiguration of atoms or molecules composing the material. For example,between in a crystalline state and in an amorphous state, there aredifferences in spectral characteristics (transmissivity, reflectivity,absorption coefficient, and the like), refractive index, and the like inoptical properties, in electric conductivity in electrical properties,and in strength, hardness, density, surface energy, and the like in theother properties. Further, it is known, when a crystal lattice hasdifferent surface orientations (or orientations) in the same crystallinestate, the respective properties vary depending on the respectiveorientation. Besides, in a thin film polycrystal formed of an aggregateof heterogeneous crystals, micro properties are different from macroproperties while the macro properties are determined depending on asynthesis of parameters of properties of the respective crystals. Inaddition, it is natural that properties of a boundary portion betweenone crystal and the other crystal are different not only from the macroproperties but also from the properties of the respective crystals.

To cite one example, it is known that semiconductor devices respectivelyusing silicon in an amorphous state, a crystalline state, and asingle-crystal state respectively have different optical properties,electrical properties, and the like.

In the case of providing a metal layer over a substrate, forming anoxide film on this metal layer, and further oxidizing the metal layerafter completing the formation of various elements on the oxide layeraccording to the present invention, it is easily expected that, in termsof a micro order, metal oxide formed at the interface between the metallayer and the oxide layer is composed of an aggregate of crystals thathave partially different properties and the state among the respectivecrystals is formed of a combination of a portion with strong cohesionand a portion with week cohesion or formed of a combination of a portionwith strong bonding power and a portion with week bonding power, and itcan be expected that peeling or separation can be brought by physicalforce.

According to the present invention, since the interface between themetal layer and the oxide layer can exist mutually in an energy state,in other words, in a bonding state within a certain range until themetal layer is oxidized, it is possible to complete a manufacturingprocess of an element such as a TFT safely without peeling untilperforming separation.

The present invention that relates to a peeling method, which isdisclosed in the specification, has a peeling method of peeling a layerto be peeled from a substrate, which is a peeling method characterizedin comprising:

a step of forming, over the substrate, a metal layer, an oxide layer incontact with the metal layer, and the layer to be peeled;

a step of oxidizing the metal layer to form a metal oxide layer;

a step of peeling the layer to be peeled that is bonded to the supportfrom the substrate that has the metal layer provided with a physicalmeans within the oxidized metal oxide layer or at an interface betweenthe metal oxide layer and the oxide layer after bonding a support to thelayer to be peeled and the oxide layer.

In the method above, the metal layer is characterized in being a singlelayer comprising an element selected from Ti, Ta, W, Mo, Cr, Nd, Fe, Ni,Co, Zr, and Zn, or one of an alloy material and a compound materialincluding the element as its main component, or a lamination layer ofthese.

Additionally, in the method above, the oxide layer in contact with themetal layer is characterized in being a silicon oxide film formed bysputtering.

Further, the layer to be peeled is characterized in including a thinfilm transistor, a photoelectric conversion element comprising PINjunction of silicon, an organic light-emitting element, an element thathas a liquid crystal, a memory element, a thin film diode, or siliconresistor element. However, a lowest layer of the element, which hascontact with the oxide layer, may include a silicon oxide film, asilicon oxynitride film, or a silicon nitride film, or may furtherinclude a lamination layer of these.

Further, in the method above, the step of oxidizing the metal film ischaracterized in being conducted with irradiation of a laser beam, heattreatment, or compound treatment of irradiation of a laser beam and heattreatment.

Further, in the method above, the laser beam is a laser beam emittedfrom a continuous wave oscillation or pulse oscillation solid laser.Typically, as the continuous wave oscillation or pulse oscillation solidlaser, there are one kind or plural kinds selected from a YAG laser, aYVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, a ruby laser, analexandrite laser, and a Ti:sapphire laser. In addition, as the othercontinuous wave oscillation or pulse oscillation laser, there are onekind or plural kinds selected from an excimer laser, an Ar laser, and aKr laser.

Further, with respect to a direction of the irradiation of the laserbeam, the laser beam may be irradiated to the metal layer form a side ofthe substrate, irradiated to the metal layer from the side of the layerto be peeled, or irradiated from the both sides.

Further, the laser beam may have any of a circular shape, a triangleshape, a square shape, a polygonal shape, an elliptic shape, and alinear shape, and may have any size on the order of a micron to amillimeter or a meter (may be a dot shape or planar shape). In addition,in the oxidizing process above, an irradiation region of the laser beammay have an overlap with a region irradiated most recently or may nothave an overlap. In addition, it is preferable that the laser beam has awavelength from 10 nm to 1 mm, more preferably, from 100 nm to 10 μm.

In the phenomenon caused in irradiating light such as a laser beam, themetal layer absorbs the light to generate heat, and it is believed thatthe generated heat energy contributes to the formation of the metaloxide layer at the interface between the metal layer and the oxidelayer. In the method introduced in related art (for example, JapanesePatent Laid-Open No. 10-125929, Japanese Patent Laid-Open No. 10-125930,Japanese Patent Laid-Open No. 10-125931), in the case of forming anelement that is the layer to be peeled on the separating layer that isan amorphous silicon film, hydrogen contained in the separating layer isdiffused and reduced when treatment is performed at a high temperatureabout from 400 to 600° C. (a temperature needed for crystallization andhydrogenation of a semiconductor silicon film) in a manufacturingprocess the element. In this case, there is a possibility thatinsufficient peeling is performed in the case of irradiating theseparating layer with a laser beam later in order to perform peeling.However, since there is no such trouble at all in the method accordingto the present invention, which enables peeling by performing oxidationtreatment of the metal layer with a laser beam irradiation, the heatprocess during forming a peel layer is not limited.

Besides, in the method above, for the metal layer, another layer such asan insulating layer may be provided between the substrate and the metallayer. However, in order to simplify the process, it is desired to formthe metal layer on the substrate in contact with the substrate.

In the case of using light such as a laser beam in the step of oxidizingthe metal layer in the present method, when the direction of theirradiation of the light is made from the side of the substrate in thecase where a material such as a metal layer or a metal pattern, whichabsorbs the light as the same level as the metal layer, exists in thelayer to be peeled, it becomes possible to prevent damage without thelayer to be peeled being irradiated with the light since the metal layerabsorbs light in the wavelength region of at least ultraviolet light,visible light, and infrared light with low transmissivity.

Further, in the case of using the heat treatment in the step ofoxidizing the metal layer in the present method, the method for the heattreatment is not limited. In particular, when RTA (Rapid ThermalAnnealing) is used, the treatment can be carried out in a short time andit becomes easier to deal with an increase in the number to be processedin the case of considering mass production.

Besides, the oxidized region of the metal layer is made to be aninterface between the metal layer and the oxide layer formed on themetal layer in the case of forming the metal layer in contact with thesubstrate while an interface between the substrate and the some layerformed between the substrate and the metal layer is additionallyconsidered in the case of forming some layer between the substrate andthe metal layer. In the latter case where it is expected that the metaloxide layer is formed at the two top and bottom interfaces the metallayer, when peeling is brought within the metal oxide layer formedbetween the metal layer and the some layer or at the interface of themetal oxide layer in peeling the layer to be peeled from the substrate,peeling may be carried out again thereafter to peel the metal layer fromthe layer to be peeled.

Another manufacturing method according to the present invention ischaracterized in that comprising:

a step of forming an insulator layer on a substrate, a metal layer incontact with the insulator layer, an oxide layer in contact with themetal layer, and a layer to be peeled including a semiconductor elementabove the oxide layer;

a step of oxidizing the metal layer to form a metal oxide layer betweenthe metal layer and the insulating layer, between the metal layer andthe oxide layer, or both between the metal layer and the insulatinglayer and between the metal layer and the oxide layer;

a step of peeling the layer to be peeled that is bonded to the supportfrom the substrate with a physical means within the metal oxide layer incontact with the insulating layer, at an interface between the metaloxide layer in contact with the insulating layer and the insulatinglayer, at an interface between the metal oxide layer in contact with theinsulating layer and the metal layer, within the metal oxide layer incontact with the oxide layer, at an interface between the metal oxidelayer in contact with the oxide layer and the oxide layer, or at aninterface between the metal oxide layer in contact with the oxide layerand the metal layer after bonding a support and the layer to be peeled.

In each of the methods above related to a manufacturing method, thesubstrate is characterized in being a glass substrate or a quartzsubstrate, and the support is a plastic substrate or a plastic basematerial.

Note that, in the specification, the physical means indicates a meansthat is recognized not chemically but physically. Specifically speaking,the physical means is a dynamical means or a mechanical means that has aprocess capable of returning to the rule of dynamics, and indicates ameans for changing some dynamical energy (mechanical energy).

However, in the methods above, it is necessary that a bonding powerbetween the oxide layer and the metal layer is set smaller than abonding power with the support when the layer to be peeled is peeledwith the physical means.

Besides, in the present invention above, it is desirable that thesubstrate is light-transmitting. Even in the case without beinglight-transmitting, there is no problem as long as light irradiation canbe performed from the side of the layer to be peeled. In the case ofperforming light irradiation from the side of the substrate, anysubstrate may be used as long as light in a region absorbed by the metallayer is transmitted.

Note that, a base material described in the specification is used forbonding and fixing the layer to be peeled with, for example, anadhesive, to which the layer to be peeled is transferred. The basematerial has a kind that is not particularly limited, and may have anycomposition such as plastic, glass, metal, or ceramics. Further, in thespecification, the support is used for being bonded with the layer to bepeeled in peeling with the physical means. The support is notparticularly limited, and may have any composition such as plastic,glass, metal, or ceramics. In addition, the base material and thesupport have shapes that are not particularly limited, and a shape witha planar surface, one with a curved surface, one with flexibility, or afilm shape may be adopted. Further, when the highest priority is placedon weight saving of a semiconductor device, it is preferable to use afilm-shaped plastic substrate as the base material, for example, aplastic substrate such as polyethylene terephthalate (PET), polyethersulfone (PES), polyethylene naphthalate (PEN), polycarbonate (PC),nylon, polyether ether ketone (PEEK), polysulfone (PSF), polyetherimide(PEI), polyarylate (PAR), polybutylene telephthalate (PBT), orpolyimide.

In the methods above related to the manufacturing method of asemiconductor device, in the case of manufacturing a liquid crystaldisplay device, the support as an opposing substrate may be bonded withthe layer to be peeled with the use of a sealing material as a bindingmaterial, or a transfer to a base material may be performed aftermanufacturing a TFT for driving a liquid crystal element, subsequentlyfollowed by a manufacturing process of the liquid crystal element. Inthe former case, an element provided in the layer to be peeled has apixel electrode, and a liquid crystal material is filled between thepixel electrode and the opposing substrate.

Further, in the methods above related to the manufacturing method of asemiconductor device, in the case of manufacturing a light-emittingdevice typified by a light-emitting device that has an EL element, it ispreferable that the support is used as a sealing member and thelight-emitting element is completely shielded from the outside to avoida substance such as moisture or oxygen, which promotes deterioration ofan organic compound layer, from penetrating from the outside. Further,when weight saving is placed at the highest priority, a film-shapedplastic substrate is preferable. However, the film-shaped plasticsubstrate has a little effect of avoiding the substance such as moistureor oxygen, which promotes deterioration of the organic compound layer,from penetrating from the outside. Therefore, a structure may beadopted, for example, in which a first insulating film, a secondinsulating film, and a third insulating film are provided on the supportto avoid the substance such as moisture or oxygen, which promotesdeterioration of the organic compound layer, from penetrating from theoutside.

Further, in the methods above related to the manufacturing method of asemiconductor device, in another case of manufacturing a light-emittingdevice typified by a light-emitting device that has an EL element, atransfer to a base material may be performed after manufacturing up to aTFT for driving a light-emitting device, subsequently followed by amanufacturing process of the light-emitting device.

Besides, the present invention has a structure obtained according to themanufacturing method above of a semiconductor device, which ischaracterized in that a semiconductor device has a metal oxide layer incontact with an adhesive over a substrate with an insulating surface andhas an element above the metal oxide layer.

In the structure above, the element is characterized in being a thinfilm transistor, an organic light-emitting element, an elementcomprising a liquid crystal, a memory element, a thin-film diode, aphotoelectric conversion element comprising PIN junction of silicon, orsilicon resistor element. Further, in the structure of the semiconductordevice above, the substrate is characterized in being a plasticsubstrate with a planar surface or a curved surface. Further, in thestructure above, the metal oxide layer is characterized in being formedby irradiation of a laser beam, heat treatment, or compound treatment ofirradiation of a laser beam and heat treatment. Note that this metaloxide layer is formed in a peeling process.

Effect of the Invention

According to the present invention, irradiation of a laser beam, heattreatment, or compound treatment of irradiation of a laser beam and heattreatment is performed to a metal layer for performing oxidationtreatment, with the result that a metal oxide layer is formed to make itpossible to peel a layer to be peeled easily from a substrate with aphysical means. In laser irradiation in the oxidation treatment, damageis not caused to a semiconductor layer since the laser irradiation isperformed to the metal layer from the substrate side in the case ofhaving no desire to damage the semiconductor layer.

Further, according to the present invention, it is possible to peelentirely with a high yield not only a layer to be peeled with a smallarea but also a layer to be peeled with a large area.

In addition, according to the present invention, peeling can be easilyperformed by a physical means, for example, by a human hand. Therefore,the process can be said to be appropriate for mass production. Further,in the case of manufacturing a manufacturing system for peeling a layerto be peeled in mass production, a large-scale manufacturing system canalso be manufactured at low cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing an embodiment mode.

FIG. 2 is a diagram showing optical properties of a metal layer.

FIG. 3 is a diagram showing a manufacturing process of an active matrixsubstrate. (Embodiment 1)

FIG. 4 is a diagram showing a manufacturing process of the active matrixsubstrate. (Embodiment 1)

FIG. 5 is a diagram showing a manufacturing process of the active matrixsubstrate. (Embodiment 1)

FIG. 6 is a diagram of peeling the active matrix form the substrate.(Embodiment 1)

FIG. 7 is a diagram showing a light-irradiation region in performingoxidation treatment of a metal layer. (Embodiment 1)

FIG. 8 is a diagram showing a sectional view of a liquid crystal displaydevice. (Embodiment 2)

FIG. 9 is a diagram showing a top view or a sectional view of alight-emitting device. (Embodiment 3)

FIG. 10 is a diagram showing a sectional structure of a pixel portion ofa light-emitting device. (Embodiment 4)

FIG. 11 is a diagram showing examples of electronic devices. (Embodiment5)

FIG. 12 is a diagram showing examples of electronic devices. (Embodiment5)

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment Mode

Hereinafter, an embodiment mode of the present invention will bedescribed.

In FIG. 1(A), reference numeral 10 denotes a substrate; 11 denotes ametal layer; 12 denotes an oxide layer; and 13 denotes a layer to bepeeled.

In FIG. 1(A), the substrate 10 may be any substrate as long as light ina wavelength region absorbed by the metal layer 11 is transmitted.

First, as shown in FIG. 1(A), the metal layer 11 is formed on thesubstrate 10. The metal layer 11 is typically a single layer comprisingan element selected from W, Ti, Ta, Mo, Nd, Ni, Co, Zr, and Zn, or analloy material or a compound material including the element as its mainconstituent, or is a lamination layer of these. The metal layer 11 has athickness set at 10 nm to 200 nm, preferably 50 nm to 75 nm.

Further, a thickness in the vicinity of a peripheral portion of thesubstrate is likely to be uneven since the substrate is fixed insputtering. Therefore, it is preferable to remove only the metal layerat the peripheral portion by dry etching. In this regard, fan insulatingfilm comprising a silicon oxynitride film may be formed to be athickness of approximately 100 nm between the substrate 10 and the metallayer 11 in order to prevent the substrate from being subjected toetching.

Next, the oxide layer 12 is formed on the metal layer 11. As the oxidelayer 12, silicon oxide or silicon oxynitride may be formed bysputtering to be a thickness nearly equal to or more than the metallayer, for example, from 10 nm to 600 nm, desirably, from 150 nm to 200nm.

Then, the layer to be peeled 13 is formed on the oxide layer 12. Thislayer to be peeled 13 may be a layer including various elements typifiedby a TFT (a semiconductor device such as a thin film diode, aphotoelectric conversion element comprising a PIN junction of silicon, asilicon resistance element, or a sensor element such as apressure-sensitive fingerprint sensor).

Next, a second substrate 15, which serves as a support for fixing thelayer to be peeled 13, is bonded with a first binding material 14. (FIG.1(B)) Note that, it is preferable, as the second substrate 15, to employa substrate with higher rigidity than that of the first substrate 10. Asthe first binding material 14, a general binding material, a two-sidedtape, or a combination thereof may be used.

Next, oxidation treatment of the metal layer 11 is performed.Specifically, irradiation of light such as a laser beam, heat treatment,or compound treatment of irradiation of light and heat treatment isperformed to oxidize the metal layer 11. In FIG. 1(C), an oxidizingprocess by light irradiation is shown.

A metal oxide layer 16 is formed by the oxidation treatment of the metallayer 11. (FIG. 1(D))

Then, the substrate 10 provided with metal layer 11 is peeled with aphysical means. (FIG. 1(E)) What shown here is the case where it isassumed that the layer to be peeled 13 has a weak mechanical strengthand the layer to be peeled 13 is broken in peeling. However, in the casewhere the layer to be peeled 13 has a sufficiently strong mechanicalstrength and the layer to be peeled 13 is not broken in peeling, thefirst binding material 14 and the second substrate 15 (support) areunnecessary in peeling and can be omitted.

FIG. 1(F) shows a state after peeling the layer to be peeled 13.

FIG. 1(G) shows a state in which a third substrate 18 that is a basematerial for transferring the layer to be peeled 13 is bonded with asecond binding material 17. The third substrate 18 has a kind that isnot particularly limited, which may have any composition such asplastic, glass, metal, or ceramics. In addition, the third substrate 18has a shape that is not particularly limited, and a shape with a planarsurface, one with a curved surface, one with flexibility, or a filmshape may be adopted.

Next, the first binding material 14 is removed or peeled to peel thesecond substrate 15. (FIG. 1(F))

Then, an EL layer 21 is formed, and sealed with a fourth substrate 19that serves as a sealing material and a third binding material 20. (FIG.1(I)) Note that the fourth substrate 19 is not particularly required aslong as the third binding material 20 has a material that issufficiently capable of blocking a substance (moisture or oxygen) thatpromotes deterioration of an organic compound layer. Here, an example ofmanufacturing a light-emitting device that uses an EL element is shown.However, the present invention is not particularly limited to the ELelement. Various semiconductor devices can be completed.

In the case of manufacturing a liquid crystal display device, a supportas an opposing substrate may be bonded with a layer to be peeled withthe use of a sealing material as a binding material. In this case, anelement provided in the layer to be peeled has a pixel electrode, and aliquid crystal material is filled between the pixel electrode and theopposing substrate. Further, the order of manufacturing the liquidcrystal display device is not particularly limited. The opposingsubstrate as the support may be bonded, a substrate may be peeled afterinjecting a liquid crystal, and then, a plastic substrate as a transferbody (a base material for transferring) may be bonded. Alternatively, asubstrate may be peeled after forming a pixel electrode, and an opposingsubstrate as a second transfer member may be bonded after bonding aplastic substrate as a first transfer body.

Also, the order of manufacturing a light-emitting device is notparticularly limited. It may be that a plastic substrate as a support isbonded after forming a light-emitting element, a substrate is peeled,and a plastic substrate as a transfer body is adhered. Alternatively, itmay be that a substrate is peeled after forming a light-emittingelement, a plastic substrate as a first transfer body is bonded, andthen, a plastic substrate as a second transfer body is bonded.

FIG. 2 shows an example of optical properties at a stage of forming ametal layer (a tungsten film: 50 nm) and an oxide layer (an siliconoxide film by sputtering: 200 nm) according to the present invention.Note that the optical properties have reflectivity and transmissivity ofincident light from this glass substrate side, measured with glass as asubstrate. Besides, absorptance is defined as a difference between 1 andthe sum of the reflectivity and the transmissivity.

As understood from FIG. 2(B), the absorption exceeds at least about 40%while the transmissivity in the wavelength region within the measurementis less than 6%. (FIG. 2(C)) Consequently, when the metal layer isirradiated with a laser beam from the substrate side, damage is notcaused to a layer to be peeled since this metal layer absorbs lightenergy, which is not transmitted.

EMBODIMENTS Embodiment 1

An embodiment of the present invention will be described with referenceto FIGS. 3 to 7. Here, a method for manufacturing a pixel portion andTFTs (n-channel TFTs and a p-channel TFT) of a driver circuit providedat the periphery of the pixel portion at the same time on the samesubstrate will be described in detail. Although an example ofmanufacturing an active matrix substrate for manufacturing a reflectiveliquid crystal display device will be shown here, there is nolimitation. When an arrangement of TFTs and a material of a pixelelectrode are appropriately changed, needless to say, it is alsopossible to manufacture a transmissive liquid crystal display device anda light-emitting device that has a light-emitting layer including anorganic compound.

A glass substrate (AN100) is used as a substrate 100. First, a siliconoxynitride layer 101 is formed on the substrate with PCVD to be athickness of 100 nm.

Subsequently, as a metal layer, a tungsten layer 102 is formed bysputtering to be a thickness of 50 nm, and without being exposed to theatmosphere, a silicon oxide layer is continuously formed by sputteringto be a thickness of 200 nm as an oxide layer 103 a. The silicon oxidelayer is formed under the conditions of using a sputtering system of aRF system, using a silicon oxide target (diameter: 30.5 cm), flowingheated argon gas at a flow rate of 30 sccm for heating the substrate,setting the substrate temperature at 300° C., the deposition pressure at0.4 Pa, the deposition power at 3 kW, and argon flow rate/oxygen flowrate=10 sccm/30 sccm.

Subsequently, the tungsten layer has a portion at the periphery of thesubstrate or an edge removed with dry etching.

Subsequently, with plasma CVD, a silicon oxynitride film 103 b(composition ratio: Si=32%, O=59%, N=7%, H=2%) manufactured from SiH₄and N₂O as material gas at a deposition temperature of 300° C. is formedto have a thickness of 100 nm, and further, without being exposed to anatmosphere, a semiconductor film with an amorphous structure (here, anamorphous silicon film) is continuously formed by plasma CVD at adeposition temperature of 300° C. with SiH₄ as deposition gas to be athickness of 54 nm.

Then, nickel acetate salt solution containing nickel of 10 ppm by weightis applied with a spinner. Instead of the application, a method ofspraying a nickel element to the entire surface with sputtering may beused. Then, heat treatment is conducted for performing crystallizationto form a semiconductor film with a crystalline structure (here, apolysilicon layer). Here, after heat treatment (500° C. for 1 hour) fordehydrogenation, heat treatment (550° C. for 4 hours) forcrystallization is conducted to obtain a silicon film with a crystallinestructure. Note that, although the technique for crystallization is usedhere, which uses nickel as a metal element that promotes crystallizationof silicon, the other known techniques for the crystallization, forexample, solid-phase growth and laser crystallization, may be used.

Next, after removing an oxide film at a surface of the silicon film withthe crystalline structure with acid such as dilute hydrofluoric acid,irradiation of a laser beam (XeCl: wavelength of 308 nm) for enhancingcrystallinity and repairing defects remaining in crystal grains isperformed in the atmosphere or in an oxygen atmosphere. As the laserbeam, an excimer laser beam with a wavelength of 400 nm or less, orsecond harmonic or third harmonic of YAG laser is used. Here, a pulsedlaser beam with a repetition frequency of approximately 10 to 1000 Hz isused, the pulse laser beam is condensed into 100 to 500 mJ/cm² in anoptical system, and irradiation is performed with an overlap ratio of 90to 95%, whereby the silicon film may have a surface scanned. Here, theirradiation of the laser beam is performed in the atmosphere with arepetition frequency of 30 Hz and an energy density of 470 mJ/cm². Notethat an oxide film is formed on the surface due to the irradiation ofthe laser beam since the irradiation is carried out in the atmosphere orin an oxygen atmosphere. Though the pulsed laser is used in the exampleshown here, continuous oscillation laser may also be used. Incrystallization of an amorphous semiconductor, it is preferable to use asolid laser that is capable of continuous oscillation and to apply thesecond harmonic to the fourth harmonic of a fundamental wave in order toobtain a crystal in a large grain size. Typically, the second harmonic(532 nm) or the third harmonic (355 nm) of Nd:YVO₄ laser (fundamentalwave: 1064 nm) may be applied. In the case of using continuousoscillation laser, a laser beam emitted from continuous oscillation typeYVO₄ laser with 10 W output is converted into a higher harmonic with anon-linear optical element. Alternatively, there is a method of puttinga crystal of YVO₄ and non-linear optical element into a resonator toemit a harmonic. Then, preferably, a laser beams is shaped so as to havea rectangular shape or an elliptical shape with an optical system at asurface to be irradiated to irradiate an object to be processed. At thistime, an energy density approximately from 0.01 to 100 MW/cm²(preferably, from 0.1 to 10 MW/cm²) is required. The irradiation may beperformed by moving the semiconductor film including a layer to bepeeled relatively to the laser beam at a rate of approximately 10 to2000 cm/s. Note that this laser beam is irradiated not from thesubstrate side but from a side of the surface of the silicon film.

In addition to the oxide film formed by the irradiation of the laserbeam, the surface is treated with ozone water for 120 seconds to form abarrier layer comprising an oxide film with a thickness of 1 to 5 nm intotal. Though the barrier layer is formed with ozone water in thepresent embodiment, an oxide film of approximately 1 to 10 nm may bedeposited to form a barrier layer with another method such asirradiation of ultraviolet light in an oxygen atmosphere for oxidizing asurface of a semiconductor film with a crystalline structure, oxygenplasma treatment for oxidizing a surface of a semiconductor film with acrystalline structure, plasma CVD, sputtering, or evaporation. Further,before forming the barrier layer, the oxide film formed by theirradiation of the laser beam may be removed.

Next, on the barrier layer, an amorphous silicon film containing anargon element, which serves as a gettering site, is formed by sputteringto be a thickness of 10 to 400 nm, in this embodiment, 100 nm. In thepresent embodiment, the amorphous silicon film containing the argonelement is formed with the use of a silicon target under an atmospherecontaining argon. In the case of using plasma CVD to form an amorphoussilicon film containing an argon element, deposition is performed underthe condition of setting a flow ratio of monosilane to argon at 1:99, adeposition pressure at 6.665 Pa (0.05 Torr), a RF power density at 0.087W/cm², and a deposition temperature at 350° C.

Then, a furnace heated to 650° C. is used to perform heat treatment for3 minutes, for gettering to reduce a concentration of nickel in thesemiconductor film with the crystal structure. Instead of the furnace, alamp annealing system may be used.

Subsequently, the amorphous silicon film containing the argon element,which is the gettering site, is selectively removed with the barrierlayer as an etching stopper, and then, the barrier layer is selectivelyremoved with dilute hydrofluoric acid. Note that since nickel tends tomove to a region with a high oxygen concentration in gettering, it isdesirable to remove the barrier layer comprising the oxide film aftergettering.

Then, after a thin oxide film is formed with ozone water on the surfaceof the obtained silicon film with a crystal structure (also referred toas polysilicon film), a mask comprising resist is formed, and an etchingprocess is conducted into a desired shape to form semiconductor layersseparated in an island shape. After forming the semiconductor layers,the mask comprising resist is removed.

According to the process above, it is possible to form the metal layer102, the oxide layer 103 a and the base insulating film 103 b over thesubstrate 100, and to perform the etching process into the desired shapeto form semiconductor layers 104 to 108 separated in the island shapeafter obtaining a semiconductor film with a crystalline structure.

Next, the oxide film is removed with an etchant containing hydrofluoricacid, and at the same time, the surface of the silicon film is cleaned.Thereafter, an insulating film including silicon as its mainconstituent, which serves as a gate insulating film 109, is formed. Inthe present embodiment, plasma CVD is used to form a silicon oxynitridefilm (composition ratio: Si=32%, O=59%, N=7%, H=2%) with a thickness of115 nm.

Next, as shown in FIG. 3(A), on the gate insulating film 109, a firstconductive film 110 a with a thickness of 20 to 100 nm and a secondconductive film 110 b with a thickness of 100 to 400 nm are formed inlamination. In the present embodiment, a tantalum nitride film with afilm thickness of 50 nm and a tungsten film with a film thickness of 370nm are sequentially laminated on the gate insulating film 109.

As a conductive material for forming the first conductive film and thesecond conductive film, an element selected from Ta, W, Ti, Mo, Al andCu, or an alloy material or a compound material including the element asits main constituent is formed. Further, a semiconductor film typifiedby a polycrystalline silicon film doped with an impurity element such asphosphorous, or an AgPdCu alloy may be used as the first conductive filmand the second conductive film. Further, the present invention is notlimited to a two-layered structure. For example, a tungsten film with afilm thickness of 50 nm, an alloy (Al—Si) film of aluminum and siliconwith a film thickness of 500 nm, and a titanium nitride film with a filmthickness of 30 nm may be sequentially laminated as a three-layeredstructure. Moreover, in case of a three-layered structure, tungstennitride may be used in place of tungsten of the first conductive film,an alloy film of aluminum and titanium (Al—Ti) may be used in place ofthe alloy film of aluminum and silicon (Al—Si) of the second conductivefilm, and a titanium film may be used in place of the titanium nitridefilm of the third conductive film. In addition, a single layer structuremay also be adopted.

Next, masks 112 to 117 comprising resist are formed in accordance withan exposure process as shown in FIG. 3(B), and a first etching processis conducted for forming gate electrodes and wirings. The first etchingprocess is conducted under first and second etching conditions. For theetching, ICP (inductively coupled plasma) etching is preferred. When ICPetching is used and the etching conditions (such as electric energyapplied to a coiled electrode, electric energy applied to an electrodeat the substrate side, a temperature of the electrode at the substrateside) are appropriately adjusted, the films can be etched into a desiredtaper shape. For etching gas, chlorine-based gas typified by Cl₂, BCl₃,SiCl₄, or CCl₄, fluorine-based gas typified by CF₄, SF₆, or NF₃, or O₂may be appropriately used.

In the present embodiment, RF (13.56 MHz) power of 150 W is applied alsoto the substrate side (sample stage) to apply a substantially negativeself-bias voltage. The electrode at the substrate side has an area witha size of 12.5 cm×12.5 cm, and the coiled electrode (quartz discprovided with a coil here) has an area with a size of a disc 25 cm indiameter. The W film is etched under this first etching condition so asto make an edge of the first conductive layer in a tapered shape. Underthe first etching condition, an etching rate to W is 200.39 nm/min, anetching rate to TaN is 80.32 nm/min, and a selection ratio of W to TaNis about 2.5. Further, under this first etching conditions, a taperangle of W is made approximately 26°. Thereafter, the first etchingcondition is changed to the second etching condition without removingthe masks 112 to 117 comprising resist, wherein CF₄ and Cl₂ are used asetching gas to have gas flow rates set at 30/30 (sccm) respectively, andRF (13.56 MHz) power of 500 W is applied to the coiled electrode with apressure of 1 Pa to generate plasma for etching performed for about 30seconds. RF (13.56 MHz) power of 20 W is applied also to the substrateside (sample stage) to apply a substantially negative self-bias voltage.Under the second etching condition in which CF₄ and Cl₂ are mixed, boththe W film and the TaN film are etched at the same level. Under thesecond etching condition, an etching rate to W is 58.97 nm/min, and anetching rate to TaN is 66.43 nm/min. Note that it is preferable toincrease etching time by approximately 10 to 20% in order to conductetching without leaving residue on the gate insulating film.

In the first etching process as described above, the masks comprisingresist have an appropriate shape, whereby the edges of the firstconductive layer and the second conductive layer have a tapered shapedue to an effect of the bias voltage applied to the substrate side. Thistapered portion may have an angle from 15° to 45°.

Thus, first shaped conductive layers 119 to 124 composing the firstconductive layer and the second conductive layer (first conductivelayers 119 a to 124 a and second conductive layers 119 b to 124 b) areformed by the first etching process. The insulating film 109 that servesas a gate insulating film is etched by approximately 10 to 20 nm, andbecomes a gate insulating film 118 that have a region thinned, which isnot covered with the first shaped conductive layers 119 to 124.

Next, a second etching process is conducted without removing the maskscomprising resist. Here, SF₆, Cl₂ and O₂ are used as etching gas to havegas flow rates set at 24/12/24 (sccm) respectively, and RF (13.56 MHz)power of 700 W is applied to the coiled electrode with a pressure of 1.3Pa to generate plasma for etching performed for 25 seconds. RF (13.56MHz) power of 10 W is applied also to the substrate side (sample stage)to apply a substantially negative self-bias voltage. In the secondetching process, an etching rate to W is 227.3 nm/min, an etching rateto TaN is 32.1 nm/min, a selection ratio of W to TaN is 7.1, an etchingrate to SiON that is the insulating film 118 is 33.7 nm/min, and aselection ration of W to SiON is 6.83. In the case where SF₆ is used asthe etching gas, the selection ratio with respect to the insulating film118 is high as described above. Thus, reduction in film thickness can besuppressed. In the present embodiment, the insulating film 118 has afilm thickness reduced by only about 8 nm.

By this second etching process, the taper angle of W becomes 70°. Bythis second etching process, second conductive layers 126 b to 131 b areformed. On the other hand, the first conductive layers are hardly etchedto become first conductive layers 126 a to 131 a. Note that the firstconductive layers 126 a to 131 a have substantially the same size as thefirst conductive layers 119 a to 124 a. In practice, in comparison withbefore the second etching process, the first conductive layer may have awidth reduced by approximately 0.3 μm, namely, approximately 0.6 μm tothe total line width. However, there is almost no change in size of thefirst conductive layer.

Further, in the case where, instead of the two-layered structure, atungsten film with a film thickness of 50 nm, an alloy film of aluminumand silicon (Al—Si) with a film thickness of 500 nm, and a titaniumnitride film with a film thickness of 30 nm are sequentially laminatedas a three-layered structure, etching may be performed for 117 secondsunder the first etching condition in the first etching process thatBCl₃, Cl₂ and O₂ are used as material gas to have gas flow rates set at65/10/5 (sccm) respectively, RF (13.56 MHz) power of 300 W is applied tothe substrate side (sample stage), and RF (13.56 MHz) power of 450 W isapplied to the coiled electrode with a pressure of 1.2 Pa to generateplasma. Under the second etching condition in the first etching processthat CF₄, Cl₂ and O₂ are used to have gas flow rates set at 25/25/10(sccm) respectively, RF (13.56 MHz) power of 20 W is applied also to thesubstrate side (sample stage), and RF (13.56 MHz) power of 500 W isapplied to the coiled electrode with a pressure of 1 Pa to generateplasma, etching may be performed for about 30 seconds. In the secondetching process, etching may be performed while BCl₃ and Cl₂ are used tohave gas flow rates set to 20/60 (sccm), RF (13.56 MHz) power of 100 Wis applied to the substrate side (sample stage), and RF (13.56 MHz)power of 600 W is applied to the coiled electrode with a pressure of 1.2Pa to generate plasma.

Next, the masks comprising resist are removed, and then, a first dopingprocess is conducted to obtain a state of FIG. 3(D). The doping processmay be conducted with ion doping or ion implantation. Ion doping isconducted under the conditions of a dosage set at 1.5×10¹⁴ atoms/cm² andan accelerating voltage set at 60 to 100 keV. As an impurity elementthat imparts n-type conductivity, phosphorous (P) or arsenic (As) istypically used. In this case, the first conductive layers and secondconductive layers 126 to 130 serve as masks against the impurity elementthat imparts n-type conductivity, and first impurity regions 132 to 136are formed in a self-aligning manner. The first impurity regions 132 to136 are doped with the impurity element that imparts n-type conductivityin the range of concentration from 1×10¹⁶ to 1×10¹⁷/cm³. Here, a regionthat has the same range of concentration as that of the first impurityregion is also called an n⁻ region.

Note that, although the first doping process is performed after removingthe masks comprising resist in the present embodiment, the first dopingprocess may be performed without removing the masks comprising resist.

Subsequently, as shown in FIG. 4(A), masks 137 to 139 comprising resistare formed and a second doping process is conducted. The mask 137 is amask that protects a channel formation region and a periphery thereof ofthe semiconductor layer for forming a p-channel TFT of a driver circuit,the mask 138 is a mask for protecting a channel formation region and aperiphery thereof of the semiconductor layer for forming one ofn-channel TFTs of the driver circuit, and the mask 139 is a mask thatprotects a channel formation region and a periphery thereof of thesemiconductor layer for forming a TFT of a pixel portion and a regionthat serves as a storage capacitor.

Under the conditions of a dosage of 1.5×10¹⁵ atoms/cm² and anaccelerating voltage of 60 to 100 keV in ion doping in the second dopingprocess, doping with phosphorous (P) is performed. Here, impurityregions are formed in the respective semiconductor layers in aself-aligning manner with the second conductive layers 126 b to 128 b asmasks. Of course, the regions covered with the masks 137 to 139 are notdoped. Thus, second impurity regions 140 to 142 and a third impurityregion 144 are formed. The second impurity regions 140 to 142 are dopedwith the impurity element that imparts n-type conductivity at aconcentration from 1×10²⁰ to 1×10²¹/cm³. Here, a region that has thesame range of concentration as that of the second impurity region isalso called an n⁺ region.

Further, the third impurity region is formed to have a lowerconcentration than that in the second impurity region due to the firstconductive layer, and is doped with the impurity element that impartsn-type conductivity at a concentration from 1×10¹⁸ to 1×10¹⁹/cm³. Notethat since doping is conducted while passing a portion of the firstconductive layer in the tapered shape, the third impurity region has aconcentration gradient in which the concentration of the impurityincreases toward the edge of the tapered portion. Here, a region thathas the same range of concentration as that of the third impurity regionis also called an n⁻ region. Furthermore, the regions covered with themasks 138 and 139 are not doped with the impurity element in the seconddoping process, and become first impurity regions 146 and 147.

Next, after removing the masks 137 to 139 comprising resist, masks 148to 150 comprising resist are newly formed and a third doping process isconducted as shown in FIG. 4(B).

In the driver circuit, by the third doping process as described above,the semiconductor layer for forming the p-channel TFT and thesemiconductor layer for forming the storage capacitor are doped with animpurity element that imparts p-type conductivity to form fourthimpurity regions 151 and 152 and fifth impurity regions 153 and 154.

Further, the fourth impurity regions 151 and 152 are required to bedoped with the impurity element that imparts p-type conductivity at aconcentration from 1×10²⁰ to 1×10²¹/cm³. Note that, although the fourthimpurity regions 151 and 152 are regions doped with phosphorous (P) inthe previous step (n⁻⁻ region), the third doping process is performedwith the impurity element that imparts p-type conductivity at aconcentration that is 1.5 to 3 times as high as that of phosphorous tohave p-type conductivity. Here, a region that has the same range ofconcentration as that of the fourth impurity region is also called a p⁺region.

Further, the fifth impurity regions 153 and 154 are formed in a regionoverlapping with the tapered portion of the second conductive layer 127a, and are required to be doped with the impurity element that impartsp-type conductivity at a concentration from 1×10¹⁸ to 1×10²⁰/cm³. Here,a region that has the same range of concentration as the fifth impurityregion is also called a p⁻ region.

According to the process above, the impurity regions that have n-type orp-type conductivity are formed in the respective semiconductor layers.The conductive layers 126 to 129 serve as gate electrodes of the TFTs.Further, the conductive layer 130 serves as one of electrodes, whichforms the storage capacitor in the pixel portion. Moreover, theconductive layer 131 forms a source wiring in the pixel portion.

Next, an insulating film (not shown in the figure) that coverssubstantially the entire surface is formed. In the present embodiment, asilicon oxide film with a film thickness of 50 nm is formed by plasmaCVD. Of course, this insulating film is not limited to a silicon oxidefilm, and another insulating film including silicon may be used as asingle layer or a laminated structure.

Then, a process of activating the impurity elements added to therespective semiconductor layers is conducted. This activation process isconducted with rapid thermal annealing (RTA) using a lamp light source,a method of irradiating a YAG laser or an excimer laser from a rearsurface, heat treatment using a furnace, or a method combined with anyof these methods.

Further, although the insulating film is formed before the activation inthe example shown in the present embodiment, the process of forming theinsulating film may be conducted after conducting the activation above.

Next, a first interlayer insulating film 155 of a silicon nitride filmis formed, and heat treatment (300 to 550° C. for 1 to 12 hours) isperformed to conduct a step of hydrogenating the semiconductor layers.(FIG. 4(C)) This process is a process of terminating dangling bonds ofthe semiconductor layers with hydrogen contained in the first interlayerinsulating film 155. The semiconductor layers can be hydrogenatedregardless of the existence of the insulating film (not shown in thefigure) of a silicon oxide film. Incidentally, since a materialincluding aluminum as its main constituent is used as the secondconductive layer in the present embodiment, it is important to apply aheat treatment condition that the second conductive layer can withstandin the process of hydrogenation. As another means for hydrogenation,plasma hydrogenation (using hydrogen excited by plasma) may beconducted.

Next, a second interlayer insulating film 156 comprising an organicinsulating material is formed on the first interlayer insulating film155. In the embodiment, an acrylic resin film with a thickness of 1.6 μmis formed. Then, a contact hole that reaches the source wiring 131,contact holes that respectively reach the conductive layers 129 and 130,and contact holes that reach the respective impurity regions are formed.In the embodiment, a plurality of etching processes is sequentiallyperformed. In the embodiment, after the second interlayer insulting filmis etched with the first interlayer insulating film as an etchingstopper, the first interlayer insulating film is etched with theinsulating film (not shown in the figure) as an etching stopper and theinsulating film (not shown in the figure) is etched.

Thereafter, a material such as Al, Ti, Mo, or W is used to form a wiringand a pixel electrode. As the material of the electrode and pixelelectrode, it is desirable to use a material with excellentreflectivity, such as a film including Al or Ag as its main constituentor a laminated film thereof. Thus, source electrodes or drain electrodes157 to 162, a gate wiring 164, a connecting wiring 163, and a pixelelectrode 165 are formed.

As described above, a driver circuit 206 that has an n-channel TFT 201,a p-channel TFT 202, and an n-channel TFT 203 and a pixel portion 207that has a pixel TFT 204 comprising an n-channel TFT and a storagecapacitor 205 can be formed on the same substrate. (FIG. 5) In thespecification, such a substrate is called an active matrix substrate forthe sake of convenience.

In the pixel portion 207, the pixel TFT 204 (n-channel TFT) has achannel formation region 169, the first impurity region (n⁻⁻ region) 147formed outside the conductive layer 129 forming the gate electrode, andthe second impurity regions (n⁺ region) 142 and 171 that function as asource region or a drain region. Further, in the semiconductor layerthat functions as one of the electrodes of the storage capacitor 205,the fourth impurity region 152 and the fifth impurity region 154 areformed. The storage capacitor 205 is formed of the second electrode 130and the semiconductor layers 152, 154, and 170 with the insulating film(the same film as the gate insulating film) 118 as a dielectric.

Further, in the driver circuit 206, the n-channel TFT 201 (firstn-channel TFT) has a channel formation region 166, the third impurityregion (n⁻ region) 144 that overlaps with a part of the conductive layer126 forming the gate electrode through the insulating film, and thesecond impurity region (n⁺ region) 140 that functions as a source regionor a drain region.

Further, in the driver circuit 206, the p-channel TFT 202 has a channelformation region 167, the fifth impurity region (p⁻ region) 153 thatoverlaps with a part of the conductive layer 127 forming the gateelectrode through the insulating film, and the fourth impurity region(p⁺ region) 151 that functions as a source region or a drain region.

Furthermore, in the driver circuit 206, the n-channel TFT 203 (secondn-channel TFT) has a channel formation region 168, the first impurityregion (n⁻⁻ region) 146 outside the conductive layer 128 forming thegate electrode, and the second impurity region (n⁺ region) 141 thatfunctions as a source region or a drain region.

These TFTs 201 to 203 are appropriately combined to form a shiftresister circuit, a buffer circuit, a level shifter circuit, a latchcircuit and the like to form the driver circuit 206. For example, in thecase of forming a CMOS circuit, the n-channel TFT 201 and the p-channelTFT 202 may be complementarily connected to each other.

In particular, the structure of the n-channel TFT 203 is appropriate forthe buffer circuit with a high driving voltage in the purpose ofpreventing deterioration due to a hot carrier effect.

Moreover, the structure of the n-channel TFT 201, which is a GOLDstructure, is appropriate for the circuit where top priority is placedon reliability.

Besides, reliability can be improved by improving flatness of thesurface of the semiconductor film. Thus, in the TFT with the GOLDstructure, sufficient reliability can be obtained even if the impurityregion that overlaps with the gate electrode through the gate insulatingfilm has an area reduced. Specifically, in the TFT with the GOLDstructure, sufficient reliability can be obtained even if the portionthat serves as the tapered portion of the gate electrode has a sizereduced.

In the TFT with the GOLD structure, a parasitic capacitance increaseswhen the gate insulating film is thinned. However, when the portion thatserves as the tapered portion of the gate electrode (first conductivelayer) has a size reduced to reduce the parasitic capacitance, the TFThas f-characteristic (frequency characteristic) improved to enable afurther high-speed operation and has sufficient reliability.

Note that, also in the TFTs of the pixel portion 207, reduction in OFFcurrent and variation can be realized by irradiation of a second laserbeam.

Further, an example of manufacturing an active matrix substrate forforming a reflective display device is shown in the embodiment. However,when the pixel electrode is formed of a transparent conductive film, atransmissive display device can be formed although the number ofphotomasks is increased by one.

After forming the display device, the metal layer 102 is irradiated witha continuous or pulsed laser beam from a side of the substrate togenerate heat for performing oxidation treatment, and a metal oxidelayer 190 is formed between the metal layer 102 and the oxide layer 103a (FIG. 6(A)). It becomes thereby possible to peel the layer to bepeeled from the substrate (FIG. 6(B)). For the laser light irradiated atthis time, an Nd:YAG laser (fundamental wave: 1064 nm) is used with anoutput of 40 W. With respect to the wavelength region, however, a laserbeam in any region may be used, as shown in FIG. 2. Besides, theirradiation of the laser beam may have a timing that is not limited tothe timing after making up the display device, but the laser beam may beirradiated in the step where peeling of the layer to be peeled isdesired. Additionally, as for a beam shape of the laser beam, a linearcontinuous wave is used this time. However, the beam shape is notlimited to this, and may be any of circular, elliptic, triangle, square,and polygonal shapes and may be any of spot and planar shapes. Further,although the process of oxidizing the metal layer is conducted withirradiation of the laser beam, oxidation treatment using heat treatmentmay be employed.

When the layer including the TFTs (the layer to be peeled), which isprovided on the oxide layer 103 a, has a sufficient mechanical strengthafter obtaining the state of FIG. 6(A), the substrate 100 may be takenoff. In the present embodiment, it is preferable to perform laserirradiation and peeling after bonding a support (not shown in thefigure) for fixing the layer to be peeled since the layer to be peeledhas an insufficient mechanical strength.

In performing the oxidation treatment of the metal element using light,a region 906 including a display device 901 (including a pixel portion902, a gate driver portion 903, a source driver portion 904, and an FPCterminal portion 905) on a substrate 900 may be irradiated with a laserbeam, as shown in FIG. 7.

Embodiment 2

Embodiment 1 shows an example of a reflective display device in which apixel electrode is formed of a reflective metal material. In the presentembodiment, an example of a transmissive display device, in which apixel electrode is formed of a light-transmitting conductive film, isshown in FIG. 8.

Since processes up to the step of forming an interlayer insulating filmare the same as those of Embodiment 1, the description thereof isomitted here. After forming the interlayer insulating film in accordancewith Embodiment 1, a pixel electrode 601 of a light-transmittingconductive film is formed. As the conductive film with transmittance,ITO (indium tin oxide alloy), indium oxide-zinc oxide alloy (In₂O₃—ZnO),zinc oxide (ZnO) film, and the like may be used.

Thereafter, contact holes are formed in an interlayer insulating film600. Then, a connecting electrode 602 overlapping with the pixelelectrode is formed. This connecting electrode 602 is connected to adrain region through the contact hole. Further, at the same time as thisconnecting electrode, source electrodes or drain electrodes of otherTFTs are also formed.

Although all of the driver circuits are formed on the substrate in theexample shown here, several ICs may be used for a part of the drivercircuits.

In this way, an active matrix substrate is formed. With the use of thisactive matrix substrate, a base material (a plastic substrate) is bondedafter peeling the TFTs to manufacture a liquid crystal module. Further,when the liquid crystal module is provided with a backlight 606 and alight guiding plate 605 and is covered with a cover 606 to complete anactive matrix liquid crystal display device that has a partial sectionalview shown in FIG. 8. The cover and the liquid crystal module are bondedwith an adhesive or organic resin. Besides, in bonding the plasticsubstrate and an opposite substrate, the substrates may be surroundedwith a frame and the space between the frame and the substrates may befilled with organic resin for bonding. Since the active matrix liquidcrystal display device is of a transmissive type, a polarizing plate 603is bonded to both of the plastic substrate and the opposite substrate.

Embodiment 3

In the present embodiment, an example for manufacturing a light-emittingdevice equipped with a light-emitting element that has a light-emittinglayer including an organic compound, which formed on a plastic substratewill be described with reference to FIG. 9.

FIG. 9(A) is a top view that shows a light-emitting device and FIG. 9(B)is a sectional view of FIG. 9(A) taken along A-A′. A dotted line 1101denotes a source signal line driver circuit, reference numeral 1102denotes a pixel portion, and reference numeral 1103 denotes a gatesignal line driver circuit. Reference numeral 1104 denotes a sealingsubstrate and reference numeral 1105 is a sealing agent. The insidesurrounded by the first sealing agent 1105 is filled with a secondtransparent sealing material 1107.

Reference numeral 1108 is a wiring for transmitting signals to be inputto the source signal line driver circuit 1101 and the gate signal linedriver circuit 1103, and receives a video signal and a clock signal froma FPC (Flexible Printed Circuit) 1109 as an external input terminal.Though only the FPC is shown in the figure here, a printed wiring board(PWB) may be attached to this FPC. A light-emitting device in thespecification includes not only a light-emitting device body but also astate where an FPC or a PWB is attached thereto.

Next, the sectional structure will be explained with reference to FIG.9(B). A driver circuit and a pixel portion are formed on a substrate1110. Here, the source signal driver circuit 1101 as the driver circuitand the pixel portion 1102 are shown. Note that, by using the peelingmethod described in Embodiment mode 1 or Embodiment 1, the substrate1110 is bonded to a base film with an adhesive layer 1100.

In the source signal line driver circuit 1101, a CMOS circuit is formedof a combination of an n-channel TFT 1123 and a p-channel TFT 1124. TheTFT forming the driver circuit may be formed of a known CMOS circuit,PMOS circuit, or NMOS circuit. Besides, although the present embodimentshows a driver integrated type in which a driver circuit is formed on asubstrate, which is not always necessary, the driver circuit can beformed not on the substrate but at the outside thereof.

The pixel portion 1102 is formed of a plurality of pixels each includinga switching TFT 1111, a current control TFT 1112, and a first electrode(anode) 1113 connected electrically to a drain of the current controlTFT 1112. Note that, although an example in which two TFTs are used forone pixel is shown, three or more TFTs may be appropriately used.

Since the first electrode 1113 has contact directly with a drain of theTFT, it is preferable to use a material layer comprising silicon, whichcan take an ohmic contact with the drain, as the bottom layer of thefirst electrode 1113, and to use a material layer with a large workfunction at the surface of the first electrode 1113, which has a contactwith a layer including an organic compound. When the first electrode ismade to be a three-laminated structure, for example, a titanium nitridefilm, a film including aluminum as its main constituent, and a titaniumnitride film, resistance as a wiring is low, and it is possible to takea favorable ohmic contact, and function as an anode. In addition, as thefirst electrode 1113, a single layer of a titanium nitride film or alaminated structure of two or more layers may be used.

Further, an insulator (referred to as a bank, a barrier, a blockinglayer, or the like) 1114 is formed on both ends of the first electrode(anode) 1113. The insulator 1114 may be formed of an organic resin filmor an insulating film including silicon. Here, as the insulator 1114, aninsulator in the shape shown in FIG. 9 is formed with the use of apositive photosensitive acrylic resin film.

In order to attain a favorable coverage, it is preferable to have anupper edge portion or a lower edge portion of the insulating material1114 formed with a curved surface that has a curvature. In the case ofusing a positive photosensitive acrylic resin film as a material of theinsulating material 1114, for example, it is preferable to make only anupper edge portion of the insulator 1114 have a curved surface with acurvature radius (0.2 μm to 3 μm). A negative photosensitive materialthat becomes insoluble in an etchant under light, and a positivephotosensitive material that becomes soluble in an etchant under lightboth can be used as the insulating material 1114.

Besides, the insulator 1114 may be covered with a protective filmcomprising an aluminum nitride film, an aluminum oxynitride film, orsilicon nitride film. This protective film may be an insulating filmincluding silicon nitride or silicon oxynitride as its main constituent,which is obtained with sputtering (DC system or RF system), or a thinfilm including carbon as its main constituent. When a silicon target isused for forming the protective film in an atmosphere containing nitrideand argon, a silicon nitride film can be formed. Alternatively, asilicon nitride target may be used. The protective film may be formedwith the use of a deposition system using remote plasma. It ispreferable to thin the thickness of the protective film as much aspossible in order to make the protective film transmit light emission.

A layer including an organic compound 1115 is selectively formed on thefirst electrode (anode) 1113 by evaporation that uses an evaporationmask or ink-jet. Further, a second electrode (cathode) 1116 is formed onthe layer including the organic compound 1115. Consequently, alight-emitting element 1118 comprising the first electrode (anode) 1113,the layer including the organic compound film 1115, and the secondelectrode (cathode) 1116 is formed. Since the light-emitting element 118emits white light in the example shown here, a color filter formed of acoloring layer 1131 and a light-shielding layer (BM) 1132 (forsimplification, an overcoat layer is not shown in the figure) isprovided.

When a layer including an organic compound, from which each of R, G andB emission is obtained, is selectively formed, full color display can beobtained without using a color filter.

In order to seal the light-emitting element 1118, the sealing substrate1104 is bonded with the first sealing material 1105 and the secondsealing material 1107. It is preferable to use epoxy resin as the firstsealing material 1105 and the second sealing material 1107. It is alsopreferable that the first sealing material 1105 and the second sealingmaterial 1107 are materials that do not transmit moisture or oxygen asmuch as possible.

In the present embodiment, as a material constituting the sealingsubstrate 1104, a plastic substrate comprising FRP(Fiberglass-Reinforced Plastics), PVF (polyvinylfluoride), Mylar,polyester, acrylic, or the like can be used besides a glass substrateand a quarts substrate. After bonding the sealing substrate 1104 withthe first sealing material 1105 and the second sealing material 1107, itis also possible to perform further sealing with a third sealingmaterial to cover a side face (exposed face).

As described above, when the light-emitting element is sealed with thefirst sealing material 1105 and the second sealing material 1107, thelight-emitting element can be shield completely from the outside andmoisture or oxygen that promotes deterioration of an organic compoundlayer can be prevented from penetrating from the outside. Accordingly, alight-emitting device with high reliability can be obtained.

Besides, when a transparent conductive film is used as the firstelectrode 1113, both-emission type light-emitting device can bemanufactured.

Although, in the present embodiment, an example of a structure(hereinafter referred to as a top-emission structure), in which a layerincluding an organic compound is formed on an anode and a cathode thatis a transparent electrode is formed on the layer including the organiccompound is shown, a structure that has a light-emitting element inwhich an organic compound layer is formed on an anode and a cathode isformed on the organic compound layer, in which light generated in theorganic compound layer is emitted through the anode that is atransparent electrode toward a TFT, (hereafter referred to as abottom-emission structure) also may be employed.

The present embodiment can be freely combined with Embodiment Mode orEmbodiment 1.

Embodiment 4

Embodiment 3 shows an example of manufacturing a light-emitting deviceequipped with a light-emitting element that has a light-emitting layerincluding an organic compound, which is formed on a plastic substrate.In the present embodiment, an explanation will be given more in detailon a sectional structure of one pixel of the light-emitting device,particularly, a connection of the light emitting element with a TFT, ashape of a barrier positioned between pixels.

In FIG. 10(A), reference numeral 40 denotes a substrate, referencenumeral 41 denotes a barrier (also referred to as a bank), referencenumeral 42 denotes an insulating film, reference numeral 43 is a firstelectrode (anode), reference numeral 44 is a layer including an organiccompound, reference numeral 45 is a second electrode (cathode), andreference numeral 46 is a TFT.

In the TFT 46, reference numeral 46 a denotes a channel formationregion, reference numerals 46 b and 46 c denote a source region or adrain region, reference numeral 46 d denotes a gate electrode, andreference numerals 46 e and 46 f denote a source electrode or a drainelectrode. Although a top gate TFT is shown here, there is no particularlimitation. An inversely staggered TFT may be employed or a staggeredTFT may be employed. Note that the reference numeral 46 f is anelectrode for connecting the TFT 46 to the first electrode 43, which hasa portion overlapping in contact with the first electrode 43.

Besides, FIG. 10(B) shows a sectional structure that is partiallydifferent from FIG. 10(A).

In FIG. 10(B), the overlap between the first electrode and the electrodeis different from the structure of FIG. 10(A). After patterning of thefirst electrode, the electrode is formed to partially overlap with thefirst electrode, whereby the first electrode is connected to the TFT.

Besides, FIG. 10(C) shows a sectional structure that is partiallydifferent from FIG. 10(A).

In FIG. 10(C), one more interlayer insulating film is further provided,and the first electrode is connected to the electrode of the TFT througha contact hole.

Besides, as a sectional shape of the barrier 41, a tapered shape may beemployed as shown in FIG. 10(D), which is obtained by etching anon-photosensitive organic resin film or an inorganic insulating filmafter exposing resist with photolithography.

Further, when positive photosensitive organic resin is used, a shape asshown in FIG. 10(E), a shape that has an upper edge portion with acurved surface can be obtained.

Further, when negative photosensitive resin is used, a shape as shown inFIG. 10(F), a shape that has an upper edge portion and a lower edgeportion with a curved surface can be obtained.

Embodiment 5

Implementing the present invention can complete various modules (anactive matrix liquid crystal module, an active matrix EL module, and anactive matrix EC module). That is to say, by implementing the presentinvention, all electronic devices with the module mounted are completed.

As such electronic devices, a video camera, a digital camera, a headmount display (goggle type display), a car navigation system, aprojector, a car stereo, a personal computer, a personal digitalassistance (mobile computer, portable telephone or electronic book) andthe like are given. FIGS. 11 and 12 show examples thereof.

FIG. 11(A) is a personal computer, which includes a main body 2001, animage input portion 2002, a display portion 2003, and a keyboard 2004.

FIG. 11(B) is a video camera, which includes a main body 2101, a displayportion 2102, a voice input portion 2103, an operation switch 2104, abattery 2105, and an image receiving portion 2106.

FIG. 11(C) is a mobile computer, which includes a main body 2201, acamera portion 2202, an image receiving portion 2203, an operationswitch 2204, and a display portion 2205.

FIG. 11(D) is a player using a record medium with a program recorded(hereinafter, referred to as a record medium), which includes a mainbody 2401, a display portion 2402, a speaker portion 2403, a recordmedium 2404, and an operation switch 2405. Further, this player uses aDVD (Digital Versatile Disc) or a CD as the recording medium, which canbe used for listening to music, seeing a movie, playing a game, andusing Internet.

FIG. 11(E) is a digital camera, which includes a main body 2501, adisplay portion 2502, an eye piece 2503, an operation switch 2504, andan image-receiving portion (not illustrated).

FIG. 12(A) is a portable telephone, which includes a main body 2901, avoice output portion 2902, a voice input portion 2903, a display portion2904, an operation switch 2905, an antenna 2906, and an image inputportion (such as a CCD or an image sensor) 2907.

FIG. 12(B) is a portable book (electronic book), which includes a mainbody 3001, display portions 3002, 3003, a record medium 3004, anoperation switch 3005, and an antenna 3006.

FIG. 12(C) is a display, which includes a main body 3101, a support base3102, and a display portion 3103.

Incidentally, the display shown in FIG. 12(C) has a middle or small sizeor large type, for example, a screen size of 5 to 20 inches. Further, inorder to form the display portion with such a size, it is preferable touse a substrate with a side of 1 m and carry out mass production bytaking many faces.

As described above, the present invention is fairly widely applied andis applicable to a manufacturing method of electronic devices in allfields. Further, the electronic devices in the present embodiment can berealized by using any combination of Embodiment Mode and Embodiments 1to 3.

1. A method of manufacturing a display device including an organic light-emitting element, comprising: forming a metal layer over a first substrate; removing a portion of the metal layer formed over a peripheral portion of the first substrate; forming an oxide layer in contact with the metal layer; forming a layer to be peeled including a thin film transistor and a first electrode over the oxide layer; forming a layer including an organic material over the first electrode; forming a second electrode comprising a transparent electrode over the layer including the organic material; separating the layer to be peeled from the first substrate; fixing a second substrate under the layer to be peeled using a second adhesive, fixing the layer to be peeled over a third substrate using a first adhesive; and wherein the third substrate has a color filter.
 2. The method according to claim 1, further comprising: irradiating a laser beam to the metal layer before separating the layer to be peeled from the first substrate.
 3. The method according to claim 1, wherein the portion of the metal layer is removed with dry etching.
 4. The method according to claim 1, wherein the metal layer is a single layer comprising an element selected from Ti, Ta, W, Mo, Cr, Nd, Fe, Ni, Co, Zr, and Zn, or one of an alloy material and a compound material including the element as its main component, or a lamination layer thereof.
 5. The method according to claim 1, wherein the first substrate is a glass substrate.
 6. The method according to claim 1, wherein the color filter overlaps with the first electrode.
 7. The method according to claim 1, wherein the second substrate comprises a metal or a plastic.
 8. The method according to claim 1, wherein the layer including the organic material is selectively formed over the first electrode by evaporation that uses an evaporation mask.
 9. The method according to claim 1, wherein the layer including the organic material is selectively formed over the first electrode by ink-jet.
 10. A method of manufacturing a display device including an organic light-emitting element, comprising: forming a metal layer over a first substrate; removing a portion of the metal layer formed over a peripheral portion of the first substrate; forming an oxide layer in contact with the metal layer; forming a layer to be peeled including a thin film transistor and an organic light-emitting element over the oxide layer; bonding a support to the layer to be peeled; separating the layer to be peeled from the first substrate after bonding the support; fixing a second substrate under the layer to be peeled using a second adhesive; and separating the layer to be peeled from the support after fixing a second substrate, fixing the layer to be peeled over a third substrate using a first adhesive; and wherein the second substrate comprises a metal or a plastic, wherein the third substrate has a color filter.
 11. The method according to claim 10, further comprising: irradiating a laser beam to the metal layer before separating the layer to be peeled from the support.
 12. The method according to claim 10, wherein the portion of the metal layer is removed with dry etching.
 13. The method according to claim 10, wherein the metal layer is a single layer comprising an element selected from Ti, Ta, W, Mo, Cr, Nd, Fe, Ni, Co, Zr, and Zn, or one of an alloy material and a compound material including the element as its main component, or a lamination layer thereof.
 14. The method according to claim 10, wherein the first substrate is a glass substrate. 